Forming roll for twin wire papermaking with axially aligned wave-shaped ribs

ABSTRACT

A forming roll for a paper-making machine of the two wire type comprises a cylindrical roll body and a multiplicity of generally corrugated-shaped ribs extending generally radially outwardly from and generally longitudinally along the surface of the cylindrical body. All of the ribs are of substantially identical wave shape along their lengths, and the ribs are substantially equally spaced apart circumferentially of the body. The ribs define a multiplicity of zig-zag, regular wave-like cells of uniform size and shape, each of which cells has a dimension longitudinally of the roll that is substantially greater than its dimension circumferentially of the roll. The medial axes of all of the cells at corresponding points circumferentially of the roll intersect cross-sectional planes of the roll at substantially the same angle such that the wave forms of all cells are substantially in phase longitudinally of the roll.

i 3,821,076 June 28,1974

1 1 FORMING ROLL FOR TWIN WIRE PAPERMAKING WITH AXIALLY ALIGNEDWAVE-SHAPED RIBS [75] Inventors: Erik Gunnar Stenberg, Karlstad;

Ernst Ingemar Emanuelsson, Skoghall, both of Sweden [73] Assignee:Aktiebolaget Karlstads Mekaniska Werkstad, Karlstad,v Sweden 221 Filed:Jan. 11,1973

21 Appl. No.2 322,690

[56] References Cited UNITED STATES PATENTS Trotman Gustafson et a1.

Primary Examiner--S. LeonBashore Assistant Examiner-Richard H. TushinAttorney, Agent, or Firm-Brumbaugh, Graves, Donohue & Raymond [57]ABSTRACT A forming roll for a paper-making machine of the two wire typecomprises a cylindrical roll body and a multiplicity of generallycorrugated-shaped ribs extending generally radially outwardly from andgenerally longitudinally along the surface of the cylindrical body. Allof the ribs are of substantially identical wave shape along theirlengths, and the ribs are substantially equally spaced apart'circumferentially of the body. The ribs define a multiplicity ofzig-zag, regular wavelike cells of uniform size and shape, each of whichcells has a dimension longitudinally of the roll that is substantiallygreater than its dimension circumferentially of the roll. The rnedialaxes of all of the cells .at corresponding points circumferentially ofthe roll intersect cross-sectional planes of the roll at substantiallythe same angle such that the wave forms of all roll.

3 Claims, 3 Drawing Figures cells are substantially in phaselongitudinally of the PAIENIEDJUNZBISH FIG.1

SHEET 1 OF 2 HBELOTB PATENTEDJUH 2 8 19741 SHEET 2 [IF 2 FIG.2

FORMING ROLL FOR TWIN WIRE PAPERMAKING WITH AXIALLY ALIGNED WAVE-SHAPEDRIBS BACKGROUND OF THE INVENTION One type of paper-making machine, whichis generally known as a two wire type machine, comprises two foraminousbelts, usually called wires, that are movable along endless paths thatinclude convergent runs in which the two wires converge in the directionof their movement toward the surface of a roll (a forming roll) and thenrun conjointly around a portion of the roll surface with the inner beltin engagement with the roll surface and with a layer of stock capturedin sandwich relation between the two wires. Stock is introduced in theform of a ribbon-like jet into the space between the wires at the zonewhere the two wires converge toward the roll. The stock intrudes betweenthe wire and drains outwardly through the outer wire and inwardlythrough the inner wire along the conjoint run where the two wires runtogether over the surface of the roll.

Effective stock drainage through the inner wire requires that theforming roll over which the wires run have as great an open area aspossible, thereby to be highly receptive to water drained through theinner wire. Various types of rolls formed with various forms of surfacestructure have been proposed. With many forms of the roll surface, thereis noticeable marking of the paper made on the machine. In some cases,the roll surface has been found to cause relatively rapid wear of theinner wire, thus increasing wire costs as well as reducing outputbecause of down-time for wire replacement.

SUMMARY OF THE INVENTION There is provided, in accordance with thepresent invention, a forming roll for a two wire type papermakingmachine that presents a large amount of open area to the wire, therebyto enhance stock drainage inwardly through the inner wire. The largeopen area is a result of providing minimum surface area of contactbetween the wire and the roll. Nonetheless, notwithstanding the smallcontact surface between the wire and roll surface, it has been foundthat wire wear is kept to a minimum. Moreover, paper made on a machinehaving a forming roll according to the invention does not show markingby the roll.

More particularly, a forming roll of a two wire type paper-makingmachine comprises a cylindrical roll body and a multiplicity ofgenerally corrugated-shaped ribs extending radially outwardly from andgenerally longitudinally along the surface of the roll body. All of theribs are of substantially identical wave shape along their lengths, andthe ribs are substantially equally spaced apart circumferentially of thebody to define a multiplicity of zig-zag, regular wave-like cells ofuniform size and shape, each of which cells has a dimensionlongitudinally of the roll that is substantially greater than itsdimension circumferentially of the roll. Corresponding points along themedial axes of all of the cells intersect common cross-sectional planesof the roll at substantially the same angle so that the wave forms ofall cells are substantially in phase with each other longitudinally ofthe roll.

In a preferred form of cell structure, the pitch distance measuredcircumferentially of the roll between DESCRIPTION OF THE DRAWINGS FIG. 1is a generally schematic side view of the forming part of a paper-makingmachine employing an embodiment of the improved forming roll;

FIG. 2 is a plan view of a segment of the surface of the roll of FIG.1', and

FIG. 3 is a view in cross-section of a small segment of the roll ofFIGS. 1 and 2 taken generally along the lines 33 of FIG. 2 and in thedirection of the arrows.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT An exemplary embodiment of apaper-making machine of the two wire type employing the improved roll,according to the present invention, comprises an inner wire 2 and anouter wire 3 that converge toward a forming roll 1 and then runconjointly over a segment of the surface of the roll. A stock deliverynozzle 4 conducts a ribbon-like jet 5 of paper-making stock into theconvergent run where the wires 2 and 3 converge toward the roll. Thevelocity of the jet is greater than the speeds of the wires, and thusthe jet is decelerated upon impinging on the wires. In addition, thevelocity of the jet develops a drainage pressure in the stock, thedrainage pressure balancing a predetermined tension maintained in theouter wire and being proportional to the wire tension and inverselyproportional to the roll radius. Drainage of the stock commences uponthe impingement of the jet with the respective wires and con tinuesthroughout the conjoint run of the two wires over the forming roll. Aportion of the drainage, usually approximately one half of the totaldrainage, is outwardly through the outer wire 3 while the remainingdrainage occuring in the forming zone occurs inwardly through the innerwire. Liquids draining through the outer wire are collected in acollector for removal through a bottom outlet; liquids draining inwardlythrough the inner wire 2 are collected and retained in the surfacestructure of the forming roll 1.

More particularly, as described in greater detail below, the surface ofthe roll 1 has a multiplicity of circumferentially separate cells 7where liquids drained through the inner wire are collected and held. Asuction box 8 within the roll is maintained under vacuum conditions thatsubstantially balance the centrifugal forces acting on the liquidscollected in the cells and tending to force the liquids back out throughthe inner wire and back into the newly formed fibrous web. The vacuum inthe'suction box 8 (or vacuums of different magnitudes in differentsections of a suction box) is communicated to the cells 7 throughpassageways or openings 10 in an inner body portion 11 of the roll. Itis not intended that any liquids be removed from the cells and drawninto the suction box through the openings l0, and this condition ismaintained by providing appropriate vacuum conditions in the suction box8 that are just sufficient to balance centrifugal force acting onliquids received in the cells. The bodies of liquid accumulating in thecells 7 throughout the conjoint run of the two wires are ultimatelyejected or thrown off in a generally tangential direction, as indicatedby the arrowed line designated by the reference numeral 12, and arecollected in a collector 13 for removal through an outlet opening in thebottom.

As may best be seen in FIGS. 2 and 3 of the drawings, a forming roll,according to the present invention, comprises an inner body 11 in theform ofa cylindrical shell having the strength and rigidity appropriatefor the size of the machine. The cells 7 that receive the drained liquidare defined by a multiplicity of generally corrugated-shaped strips orribs 14 which are, preferably, welded onto the surface of the body 11.The outer edges of the ribs 14 form the roll surface and support thewires. In a preferred embodiment, the ribs 14 extend continuouslylongitudinally across the cylindrical body over that portion of theinner wire through which stock drainage occurs. As illustrated in FIG.2, each end of the roll may have a flange or shoulder 17 that defines aface 15 at the end of the drainage portion of the roll, the ribs 14abutting and being joined to the face 15. The major surface of the rollbody 11 is a circular cylinder of a diameter less than that of theshoulders and the surface defined by the edges of the ribs and isdesignated by the reference numeral 16, the surface of the body thusdefining the inner or base wall of each cell 7 that is further definedby the respective ribs 14.

As may best be seen in FIG. 2, considered in conjunction with FIG. 1,all of the ribs 14 are of substantially identical wave shape along theirlengths, and the ribs are substantially equally spaced apartcircumferentially of the body. Thus, the ribs 14 define a multiplicityof zig-zag, regular wave-like cells 7 that are of uniform size andshape. Each of the cells has a dimension longitudinally of the roll thatis substantially greater than its dimension circumferentially of theroll. Indeed, it is preferred that the cells extend continuously fromend to end of the roll between the flanges 17 at opposite ends of therolls.

At corresponding points circumferentially of the roll the medial axes ofall cells intersect radial crosssectional planes of the roll atsubstantially the same angles so that the wave forms of all rolls aresubstantially in phase longitudinally of the roll. In other words, theribs and the cells that they define are geometrically and dimensionallyoriented to form a regular wave pattern with corresponding points ineach such wave pattern located in a common plane perpendicular to theaxis of the roll. It will also be observed in FIG. 2 that the passages10 are located to communicate with each cell, the holes being located inzig-zag rows that correspond in shape substantially to the wave form ofthe cells.

Preferably, the pitch distance between the medial axes of the cellsmeasured circumferentially of the roll is substantially equal to theamplitude of the wave forms of the cells between adjacent loops. Thisplaces the corresponding trailing loops of a rib defining a leading(relative to roll rotation) end of a given cell generally inlongitudinal alignment with the leading loops of the rib defining thetrailing end of such cell.

The above-described embodiment is intended to be merely exemplary, andmany variations and modifications of the embodiment may be made by thoseskilled in the art without departing from the spirit and scope of theinvention. All such variations and modifications are intended to beincluded within the scope of the invention as defined in the appendedclaims.

We claim:

1. In a paper-making machine of the type having a r0- tatable roll, aninner foraminous belt and an outer foraminous belt movable along endlesspaths that include a convergent run in which they converge in thedirection of their movement toward the roll surface and a conjoint runin which they run conjointly around a portion of the roll surface withthe inner belt in engagement with the roll surface, and a stock deliverynozzle for introducing a ribbon-like jet of paper-making stock underpressure between the belts at the convergent run thereof, whereby alayer of stock is received between the belts and moves with them alongtheir conjoint run for drainage outwardly through the outer belt andinwardly through the inner belt along such conjoint run, an improvementwherein the rotatable roll comprises a cylindrical body and amultiplicity of generally corrugated-shaped ribs extending radiallyoutwardly from and generally longitudinally along the surface of thecylindrical body, all ribs being of substantially identical wave shapealong their lengths and the ribs being substantially equallyspaced-apart circumferentially of the body to define a multiplicity ofzig-zag regular wavelike cells of uniform size and shape, each of whichcells has a dimension longitudinally of the roll that is sub; stantiallygreater than its dimension circumferentially of the roll, and all ofwhich cells have medial axes that at corresponding pointscircumferentially of the roll intersect radial cross-sectional planes ofthe roll at substantially the same angle such that the wave forms of allcells are substantially in phase longitudinally of the roll.

ward stock drainage through the belt occurs.

1. In a paper-making machine of the type having a rotatable roll, aninNer foraminous belt and an outer foraminous belt movable along endlesspaths that include a convergent run in which they converge in thedirection of their movement toward the roll surface and a conjoint runin which they run conjointly around a portion of the roll surface withthe inner belt in engagement with the roll surface, and a stock deliverynozzle for introducing a ribbon-like jet of paper-making stock underpressure between the belts at the convergent run thereof, whereby alayer of stock is received between the belts and moves with them alongtheir conjoint run for drainage outwardly through the outer belt andinwardly through the inner belt along such conjoint run, an improvementwherein the rotatable roll comprises a cylindrical body and amultiplicity of generally corrugatedshaped ribs extending radiallyoutwardly from and generally longitudinally along the surface of thecylindrical body, all ribs being of substantially identical wave shapealong their lengths and the ribs being substantially equallyspaced-apart circumferentially of the body to define a multiplicity ofzig-zag regular wave-like cells of uniform size and shape, each of whichcells has a dimension longitudinally of the roll that is substantiallygreater than its dimension circumferentially of the roll, and all ofwhich cells have medial axes that at corresponding pointscircumferentially of the roll intersect radial cross-sectional planes ofthe roll at substantially the same angle such that the wave forms of allcells are substantially in phase longitudinally of the roll.
 2. Theimprovement according to claim 1 wherein the pitch distance between themedial axes of the cells measured circumferentially of the roll issubstantially equal to the amplitude of the wave forms of the cellsbetween adjacent loops thereof.
 3. The improvement according to claim 1wherein the ribs and the cells defined thereby extend substantially theentire length of the part of the roll where inward stock drainagethrough the belt occurs.